The present invention relates to a blade for a gas turbine engine, particularly to fan blades, or compressor blades, of gas turbine engines.
One problem with fan blades of gas turbine engines is that the leading end of the aerofoil portion of the fan blades suffers from erosion due to impact from foreign objects drawn into the intake of the gas turbine engine. The erosion of the leading end of the aerofoil portion of the fan blade results in blunting of the leading end of the aerofoil of the fan blade and a consequential loss of efficiency of the fan blade.
It is known in the prior art to reduce erosion of gas turbine blades by providing an erosion resistant coating on the surface of the blades, for example our published European patent application EP0674020A, published Sep. 27, 1995. However, the application of an erosion resistant coating results in blunting of the leading end of the aerofoil of the fan blade and a consequential loss of efficiency of the fan blade.
Accordingly the present invention seeks to provide a novel blade for a gas turbine engine which overcomes the above mentioned problems.
Accordingly the present invention provides a gas turbine engine blade comprising an aerofoil portion having a convex surface, a concave surface, a leading end and a trailing end, the leading end comprising a leading edge arranged between a first leading end portion and a second leading end portion, the first leading end portion being arranged on the convex surface side of the aerofoil portion and the second leading end portion being arranged on the concave surface side of the aerofoil portion, the leading edge being formed of a harder material than the material of the first and second leading end portions such that the leading end of the aerofoil portion retains a taper from the first and second leading end portions to a relatively sharp leading edge.
Preferably the blade is a fan blade or a compressor blade.
Preferably the fan blade comprises at least three sheets diffusion bonded together, at least one of the sheets defining the convex surface, at least one of the sheets defining the concave surface and at least one of the sheets forming a corrugated structure between the convex surface and the concave surface and extending to the leading end of the aerofoil portion.
Preferably the at least one sheet forming a corrugated structure between the convex surface and the concave surface and extending to the leading end of the aerofoil portion being formed of a harder material than the at least one sheet defining the convex surface and the at least one sheet defining the concave surface.
Preferably the at least three sheets are formed of titanium alloy.
Preferably the at least one sheet forming a corrugated structure between the convex surface and the concave surface and extending to the leading end of the aerofoil portion being formed of a harder titanium alloy than the at least one sheet defining the convex surface and the at least one sheet defining the concave surface.
Alternatively the at least three sheets may be formed of the same titanium alloy, the at least one sheet forming a corrugated structure between the convex surface and the concave surface and extending to the leading end of the aerofoil portion being formed of a hardened titanium alloy and the at least one sheet defining the convex surface and the at least one sheet defining the concave surface being formed of unhardened titanium alloy.
Alternatively the at least one sheet forming a corrugated structure between the convex surface and the concave surface and extending to the leading end of the aerofoil portion being formed of a harder alloy than the at least one sheet defining the convex surface and the at least one sheet defining the con cave surface, the at least one sheet defining the convex surface and the at least one sheet defining the concave surface being formed of titanium alloy.
Preferably the at least one sheet forming the corrugated structure between the convex surface and the concave surface and extending to the leading end of the aerofoil portion extending beyond the at least one sheet defining the convex surface and the at least one sheet defining the concave surface.
Alternatively a strip of material may be positioned between the at least one sheet forming the convex surface and the at least one sheet forming the concave surface, the strip of material being formed of a harder material than the at least three sheets.
Alternatively a strip of material may be positioned at the leading end of the aerofoil portion, the strip of material being formed of a harder material than the at least three sheets.
The strip of material may extend beyond the leading end of the aerofoil.
The strip of material may be located in a slot at the leading end of the blade.
The strip of material may be welded, diffusion bonded or brazed in the slot.